In 1963, Kemmy joined the Labour Party and worked as a trade unionist. He was a member of the party's National Administrative Council, and its Director of Elections in 1969. He resigned from the party in 1972 because of conflict with local Labour TD Stephen Coughlan. Taking advantage of a change in the law which removed the ban on council employees standing for election as councillors, he was elected to Limerick City Council in 1974. He had pledged not to wear the formal robes of a councillor, saying that "While some councillors act like clowns, there is no need to dress like them."

In 1975 Kemmy founded the Limerick Family Planning Clinic. At the time, it was illegal to sell condoms in Ireland and the clinic was condemned by the Catholic Church.

Shortly before his death, Kemmy edited the acclaimed book The Limerick Anthology which featured the work of his admirer, Frank McCourt.[2]

Kemmy died on 25 September 1997, following a short illness. The by-election for his seat was held on 11 March 1998 and was won by the Labour Party candidate and former Democratic Socialist Party colleague Jan O'Sullivan.

The College of Business in the University of Limerick has been named in his memory in 2003 as the "Kemmy Business School".[4] The University College Cork branch of the Labour Party is named after him. The city council had proposed in 1999 to name a new bridge after Kemmy, but it was renamed the Abbey Bridge.[5] In 2000 the Limerick City Museum was renamed the Jim Kemmy Municipal Museum.[6] Kemmy's life is profiled in a major biography: Jim Kemmy - stonemason, trade unionist, politician, historian by Brian Callanan (Liffey Press, 2011).